Condensation of isoaldehydes with lower aliphatic aldehydes



United States Patent'() CONDENSATION F ISOALDEHYDES WITH LOWER ALIPHATIC ALDEHYDES Hugh J. Hagemeyer, Jr., and Glenn V. Hudson, Longview, Tex., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application October 17, 1955 I Serial No. 541,052

8 Claims. (Cl. 260-601) This is a continuation-in-part of applicants copending application Serial No. 468,586, filed November 12, 1954.

This invention is concerned with a new and novel process for the production of unsaturated aldehydes by the reaction of isoaldehydes with lower aliphatic aldehydes. It is particularly concerned with a process wherein an aliphatic aldehyde containing only one available hydrogen on the alpha carbon is condensed withga lower aliphatic aldehyde containing two available hydrogen atoms on the alpha carbon atom to form an unsaturated aldehyde. It is concerned with a process wherein an isoaldehyde and a lower aliphatic aldehyde are reacted in the presence of an alkaline catalyst under particular conditions as regards pressure and temperature. It is specifically concerned with a process for the production of unsaturated aldehydes by reacting isobutyraldehyde and Z-methylbutyraldehyde with lower aliphatic aldehydes at temperatures from 60150 C. in the presence of strongly alkaline catalysts. The invention is further concerned with a process wherein the lower aliphatic aldehyde is reacted in the presence of an excess of the isoaldehyde and an alkaline catalyst at a temperature in the range of 60150 C. It is further specifically concerned with a process for the production of 2-ethyl-4-methylpentenal, Z-propyl-4-methylpentenal, 2-isopropyl 4-methylpentenal, 2,4-dimethylhexenal, 2-ethyl-4-methylhexenal, 2-isopropyl-4-methylhexenal and 2-propyl-4-methylheirenal. This invention is further concerned with the condensation of the mixed aldehyde stream produced by the oxonation of butenes to produce IO-carbon enals. The oxonation of butene streams comprised of butenes-1 and 2 and isobutylene results in the formation of a mixture of n-valeraldehyde, Z-methylbutyraldehyde and 3-methylbutyraldehyde. This invention is concerned with ;a new and novel process whereby all three of these valeraldehydcs are condensed and converted to IO-carbon enals. Thegparticular novelty resides in the condensationof 2- methylbutyraldehyde with n-Valera'ldehyde and 3 -methylbutyraldehyde to form unsaturated enals. j

The invention is further concerned with the new compositions of matter produced'by the hydrogenation of the corresponding 'enals to the corresponding anals. These new compositions ofv matter include 2-ethyl-4- methylpentanal, 2-propyl-4-methylpentanal, 2,-isopropyl- #Emethylpentanal, 2,4-dimethylhexanal, 2-ethyl-4-methylhexanal, Z-isc-propyl-4-methylhexanal, and 2-propyl-4- inethylhexanala i The invention is also concerned with the preparation o f the new compositions of matter produced by 1116 00111- pletehydroge'nation of ,the ena'lsto produ'cethe correspending anols. The new and valuable alcohols produced by the process of the present invention include 2-ethyl-4- methylpentanol, 2-propyl-4-methylpentanol, 2-isopropyl- 4-methylpentanol, 2,4-dimethylhexanol, 2-ethyl-4-methylhex-anol, 2-isopropyl-4-methylhexanol, and 2-propyl-4- methylhexanol.

The invention is "still further concerned with the preparation of new and valuable vinyland cellulosic plasticand to a CH group easier than to a wherein isobutyraldehyde adds hyde. In the presence p beformed.

izers by the reaction of these new alcohols with suitable dibasi'c acids to form the corresponding succinates, adipates, sebacates, azelates, and phthalates.

Lieben, Monat fiir Chemie, 22, 291-298 (1901) states that the rule for aldehyde addition is that the'aldehyde group adds to a CH group easier than to a CH group CH group. Thus it would be expected that the addition of an aliphatic aldehyde would take place at the alpha carbon of the isoaldehyde. We have now discovered conditions wherebythe addition takes place at the CH group rather than the CH group. Kohn, Monat fiir Chemie, 22, 23-24 (1901) has claimed the formation of a trace of a mixed aldol to p'ropionaldehyde. Kohn states that the crude product is nondistillableand is comprised mainly of isobutyr-aldol and propionaldol. The article further states that the separation of these aldo'ls is done only with great difliculty. We have 'asubs'tantially improved process. The formation of isobutyraldol is eliminated by operating at reflux temperatures and using a strong alkaline catalystrather than potassium carbonate. The formation of propionaldol is also substantially reduced by employing excess isoaldehyde which causes the aliphatic aldehyde to react immediately as added. The process of the present invention makes use of the discovery that easily dehydratable aldols-ofisoaldehydes (Z-methylbutyraldehyde and isobutyraldehyde) and lower aliphaticaldehyde's are prepared by adding the isoaldehyde to the alpha carbon of the lower aliphatic aldehyde. This is accomplished by oper-ating under particular conditions of temperature and at no mal or increased pressures. It is further based upon the discovery that the alternate aldol condensation products wherein the lower aliphatic aldehyde adds to the alpha carbon of the isoaldehyde revert to the originalmonomeric aldehydes in the presence of a strong alkaline catalyst at temperatures of 50-150 and at normal or increased pressuresj In Equations 1 through 4 the four possible aldol products from the homo and hetero condensations of isoaldehydes and lower'aliphatic aldehydes are shown.

R is hydrogen, alkyl, or aryl; R can also behigher alkylresidues; i p p In an earlier application of one of the applicants, Serial No. 439,865, filed'lune 28, 1954, now S."I atent No 2,811,562, it has been shown that the aldolprodu cti3 is formed to the exclusion of all others by carrying out the condensation at temperatures from 60-90 C. presence of an alkali metal carbonate catalyst. The complete suppression of any of the aldolproduct 1 was ac complished by operating in the presence of excess isoaldef of strongly alkaline catalyst such as sodium and potassium hydroxidefand sodium and potassium cyanide and operating at temperatures in the range of 0,'40 C., all of the aldol products 1 through 4 can is 'usually methyl all:

man oes -We have-nowdiscovered that by operating under strong- 1y alkaline conditions and at temperatures in excess of 60 C. that only the easily dehydrated aldol products 1 and late-formed. As mentioned-above, operating in the presence of excess isoaldehyde the formation of aldol product 1 can be practically completely suppressed. By operating at the elevated temperatures employed in carrying outthe aldol condensation of isoaldehyde with lower aliphatic aldehydes, the product formed is the unsaturated enal-resulting-from the dehydration'of the primary aldol product.

cacaonncnto 11,0 =ortcn=oncno "R' on n The process of the present invention has been applied to the reaction of isobutyraldehyde with n-butyraldehyde to form 2-ethyl-4-methylpentenal, isobutyraldehyde with nyaleralde'hyde to form 2-propyl-4-methylpentenal and isobutyraldehyde with 3-.methylbutyraldehyde to form 2- isopropyl-4 methylpentenal. In a similar fashion isovaleraldehyde (Z-methylbutyraldehyde) has been condensed withpropionaldehyde to form 2,4-dimethylhexenal, with n-butyraldehyde to form V2-ethyl-4-methylhexenal, with 3- methylbutyraldehyde to form 2-isopropyl-4-methylhexenaland with n-valeraldehyde to form 2-propyl-4-tnethylhexenal. 7 Although it is possible to carry out the condensation of isoaldehydes with lower aliphatic aldehydes containing from 2 to 6 carbon atoms, the preferred condensations are those involving two particular isoaldehydes, namely isobutyraldehyde and Z-methyllzputyraldehyde, with three, .four and five-carbon aldehydes. In this preferred range .the highest conversions and yields to the dehydratable mixed aldol product (Equation 2) are realized. Thus the homocondensation reactivity of the acetaldehyde is so much greater than its hetero condensation reactivity that the principal product, where the isoaldehyde is reacted with acetaldehyde under the conditions of the present invention, is crotonaldehyde. In;contrast the condensations carried out in accordance with the present invention between isoaldehydesand 4 and S-carbon adiphatic.aldehydes resultin the formation of easily dehydratable mixed aldol products as the principal product.

The easily; dehydratable aldolproducts of isoaldehydes with lower aliphatic aldehydes such as butyraldehyde, nvaleraldehyde, 3-methylbutyraldehyde have been made by feeding a mixture of the aldehyde to a hot solution 'of sodium hydroxide. Although the concentration of alkali used is not critical, a strong alkaliisnecessa-ry, and it is generallypreferred to use a 210% sodium hydroxide or potassium hydroxide solution. to organic layer can vary. within wide limits in the aldol reactor, that is; as much as 95 alkali-layer in contact with the organic layer may be used or as little as 30% alkali layer and 70% organic layer may be maintained. Reactiontemperatures varying from 50-150 C. have been used and we have foundthat the optimum results are usually obtained in the temperature range of 90-410 C. At temperatures below this preferred range, the formation of the aldol product resulting from the hornocondensationof the lower aliphatic aldehyde with itself is formed in increasing amounts and at temperatures above 110" C.there is considerable yield loss due to the formation of Tischenko products and the Cannizzaro reaction. The ratio of isoaldehyde to lower aliphatic aldehyde may vary from as little as l/l to 1100/1. Pressures employed may-vary fromgatmospheric to those pressures requ t ma nta nthedesir ex e s of o ldehy efi the aldol reactor at the elevated temperaturesemployedfor the condensation reaction.

By operating in the preferred-temperature range and using strongly alkaline catalyst solutions, none of the aldol products representing the addition of a lower aliphatic aldehyde to the alpha carbon of the isoaldehyde (Reac- The ratio of water layer the following 7 EXAMPLE 1 2-m ethylbutymldehyde plus n-valeraldehyde Seventeen hundred twenty grams of isovaleraldehyde (Z-methylbutyraldehyde) and 860 g. of n-valeraldehyde were mixed and fed to the suction side of a pump which was cycling a 5% solution of sodium hydroxide at 96 C. The aldehyde mixture was fed in over a three-hour period and the unreacted valeraldehydes were distilled out, comdensed and recycled to the reactor. An organic-water ratio in the reaction system of 30 was maintained and the reactor was'overflowed to a decanter, the organic layer decanted continuously and the water layer returned to the reactor.

The total reaction time required was 5.2 hours. The crude aldol product was-steam distilled from 2% caustic and'the steam distillate was dried and distilled. The unreacted valeraldehydes were stripped off. The crude enal product was distilled'on a l00-plate column at 16 to 1 reflux. Ninety-six percent of the normal valeraldehyde was reacted and was converted to 2-propyl- 4-methylhexeual [CH CH CH(CH CH=C (C l-I CHO] with the yield based on isovaleraldehyde of 94%. 2- propyl-4-methylhexenal boils at 200 C.,

dgg 0.84445, N 3 1.4.5275 This is a new composition of matter.

EXAMPLE 2 Z-methyl butymldehyde plus 3-methyl butyraldehyde was obtained and the yield based on Z-methylisobutyraldehyde was 96%. 2-isopropyl-4-methylhexenalboils at 192 C. This is a new composition of matter.

EXAMPLE 3 Z-methyl butyraldehyde plus n-butyraldehyde Seventeen-hundred twenty grams of Z-methylbutyraldehyde and 720 g. of n-butyraldehyde were mixed and fed to the suction side of a circulatory pump which was cycling a 2% solution of sodium hydroxide at 93-95 C. The aldehyde mixture was fed in over a four-hour period and the unreacted aldehydes were condensed and recycled to the reactor. The total reaction time was 3 hours. The crude product decanted from the caustic solutionwas steam distilled from 2% sodium hydroxide solution and theunreacted aldehydes were stripped off from the steam distillate. The crude enal product was dried and distilled on a. loQ-plate column at 16-to-1 reflux. A 72% 99nversion of n-butyraldehyde to 2-ethyl-4-methylhexanal [CH CH CH(CH CH=C(C H CHO] was realized and the yield based on n-butyraldehyde was rtop h p es ate '5 62%. A 34% yieldof n-butyraldehyde. to Z-ethylhexenal was also realized. 2-ethyl-4-methylhexenal boils at 187 C.,

This is a new composition of matter. EXAMPLE 4 Isobutyraldehyde plus n-valeraldehyde Fourteen-hundred forty grams of isobutyraldehyde and 860 g. of n-valeraldehyde were mixed and fed to the discharge side of a circulatory pump which was cycling a 2% solution of sodium hydroxide at 9396 C. The aldehyde mixture was fed in over a 2-hour period and the unreacted aldehydes distilling from the reactor were condensed and recycled to the reactor. The reactor was overflowed continuously and the organic layer decanted and steam distilled from 2% caustic. Unreacted aldehydes were stripped oif and the crude enal product was dried and distilled on a l-plate column at 16-to-1 reflux. An 87% conversion to 2-propyl-4-methylpentenal This is a new composition of matter.

EXAMPLE 5 Isobutyraldehyde plus 3-methyl butyraldehyde Fourteen-hundred forty grams of isobutyraldehyde and 860 'g. of 3-methylbutyraldehyde were mixed and fed to the suction side of a circulatory pump which was cycling a 2% solution of sodium hydroxide heated to 92-95 C. The aldehyde mixture was fed in over a three-hour period and unreacted aldehydes which distilled from the reactor were condensed and recycled to the reactor. The total reaction time was 3 hours. The reactor was continuously overflowed, the organic layer was separated and the water layer was returned to the reactor system. The organic layer was distilled from a 2% caustic solution and the steam distillate was stripped of unreacted aldehydes. The crude enal product was dried and distilled on a 100-p1ate column at 16-to-1 reflux. A 67% conversion to 2-isopropyl-4-meth-. ylpentenal was obtained and the yield based on isobutyraldehyde was 87%. 2-isopropyl-4-methylpentenal distills at 175 C. This is a new composition of matter. The conversion of 3-methylbutyraldehyde to 2-isopropyl- S-methylhexenal was 28%. 2-isopropyl-5-methylhexenal distills at 190 C. p

. 1 EXAMPLE6 Mixed valeraldehydes from butenes 1 and 2 By oxonation of a97% butene fraction containing 48% butene-1 and 49% butene-,Z there wasobtained a 2.6-,to- 1 mixture of n-valeraldehyde and isovaleraldehyde (Z-methylbutyraldehyde). This aldehyde mixture was fed directly to the discharge side of a circulatory pump which was cycling a 5% solution of sodium hydroxide jat 9296 C. The unreacted aldehydes distilling from the reaction mixture were condensed and recycled to the reactor. A portion of the reactor liquid was overflowed continuously, the organic layer decanted and fed to a column where it was distilled from 2% caustic; The water layer from the reactor decanter was returned to the reactor. The total reaction time was 4 hours. Distillation of the product gave a 52% yield to 2-propyl-4-meth-- ylhexenal, boiling point 200 C., and a 39% yield to 6 E LE? Mixed valeraldehydes from butenes arid isobutene A refinery butane-butene stream was treated to separate the butene stream containing 37% isobutylene, 26% butene-1 and 34% butene-2. This material was oxonated with a 1-to-1 mixture of carbon monoxide and hydrogen at -145 C. and 2500-3000 p. s. i. Five thousand grams of the aldehyde mixture as obtained from the continuous oxo reactor contained 1635 grams of 3- methylbutyraldehyde, 2110 grams of n-valeraldehyde and 1255 grams of 2-methylbutyraldehyde. This mixture was fed to the suction side of a circulatory pump which was cycling a 5% solution of sodium hydroxide at 92-95 C. The organic-to-water ratio in the reactor was maintained at 70-30 and the total liquid volume in the reactor was 1400 ml. The unreacted S-carbon aldehydes which distilled out of the reactor were condensed and recycled to the suction side of the pump. A portion of the reactor liquid was continuously overflowed to a de canter and the water layer returned to the reactor. The organic layer was fed to a steam distillation column and steam distilled from 2% caustic solution. After stripping oif unreacted valeraldehydes the crude enal product was dried and distilled on a 100-plate column at 16-to-1 reflux. The conversion of valeraldehydes to IO-carbon enals was'91% and the total yield was 4296 grams. The enal fraction contained 1396 grams of 2-propyl-4-methylhexenal, 770 g. of 2-isopropyl-4-methylhexenal, 991 g. of 2-isopropyl-S-methylhexenal and 1137 g. of 2-propylheptenal. The boiling range of the enal fraction was 192-208 C.

EXAMPLE 8 Z-methyl butyraldehyde plus propionaldehyde dig 0.8490, Ni? 1.45144 was obtained. This is a new composition of matter.

EXAMPLE 9 Z-methyl valemldehyde+n-hexalaehyde The oxonation of pentene-l normal 'and isohexaldehyde. The iso and normal hexaldehydes were reacted as in Example 8 to give a 62% yield of 2-butyl-4-methylheptenal and 29% yield of 2- butyloctenal.

gave a 1.6/1 mixture of 2-alkyl-4-methylpentauals and 2-alkyl-4-methylhexahals I 1 Allof the enals prepared in the above "examples were hydrogenated to form the corresponding anals .by'carrying out the hydrogenation in the presence of'Raney nickel at 6070 C. and at moderately elevated pressures in the. range 50 to 1500 p. s. i. The anals produced according to the process of this invention include 2,4-dim'ethylhexanal, 2-ethyl-4-methylhexanal, 2-isopropyl-4-methylhexanal, Z-propyl-4-methylhexanal, 2-propyl-4-methylpentanal, 2-propyl-4-methylpentanal, 2 isopropyl-4-methyl pentanal and 2-ethyl-4-methylpentanal. These conversions are illustrated in the following examples.

EXAMPLE 1 0 W earmarks a Ptt pth 'q ri a h q 'qee' had been used the reaction was stopped and the autoclave discharged. The crude anal product was filtered, ashed withwater, dried and distilled. A 78%; conversion to 2-propyl-4-methylpentanal boiling point 170 C. was obtained. This is a new composition of matter.

EXAMPLE -11 Operating in the same manner as reported in Example 8, the following results wereobtained: 2-ethyl-4-methylpentenal was converted 86% to 2-ethyl-4-methylpentanal, boiling point 153 C. 2-isopropyl-4-methylpentenal gave an 81% conversion to2-isopropyl-4-methylpentanal, boiling point 166 C. 2-ethyl-4rnethylhexenal gave a 78% conversion to 2-ethyl-4-methylhexanal, boiling point178 C. 2-isopropyl-4-rnethylhexenal gave an 89% conversion to 2-isopropyl 4 methylhexanal, boiling point 183 'C. 2-propyl-4-nt'ethylhexenal gave a 91" conversion to 2-propyl-4-methylhexanal, boiling point 192 C. 2-,4-dirnethylhexenal gave a 72% conversion to 2,4- dimethylhexanal, boiling point 162 C. All of these anals are newconipositions of matter. They are important intermediates in the preparation of saturated aliphatic acids useful in plasticizers, detergents, and as solubilizing agents for metal oxides used in paint driers and oil. bodying.

EXAMPLE 11a Seven hundred fifty grams of 2-ethyl-4-rnethylpentanal was charged to an oxidation column 5' high and 1" I. D. Air was admitted through a dispersion plate at the bottom of the column and the anal was oxidized at 3040 C., cooling as reguired to maintain this temperature. The oxidation found to have occurred at the end of 4 hours as indicated'by the percent oxygen in the exit air, was greater than 18 percent.

Distillation was carried out on a 30-plate bubble cap column and after removing unchanged anal, 576 grams of 2-ethyl-4-methylpentanoic acid was obtained. 2- ethyl-4-methylpentanoic acid is a clear, colorless liquid, boiling point 218-220 C. at 760 mm.

EXAMPLE 1 1b The cobalt and lead salts of 2-ethyl-4-methylpentanoic acid were formed by fusing a suspension of the metal oxide in the organic acid and driving off water. The cobalt and lead salts were 7 and 9 percent more soluble respectively in toluene than the corresponding 2-ethylhexoate salts.

EXAMPLE 11c A three-liter, three-necked flask was fitted with a stirrer and water trap. The flask was charged with 3 moles (438g) of 2,2,4-trimethyl l,3-pentanediol, 6.5 moles of 2-ethyl-4-methylpentanoic acid, 2 ml. of sulfuric acid and 500 ml. of benzene. The theoretical quantity of water was azeotroped out. The mixture was cooled, washed with 5% sodium hydroxide, washed with water and stripped under vacuum.

The di-Z-ethylhexyl ester of the diol was prepared in the same manner. The mechanical properties of Geon 101 (a polyvinyl chloride polymerB. F. Goodrich Co.) at plasticizer concentrations of 40 P. H. R. (parts per hundred of rubber) are shown below.

.....*s. 1 As low. temperature lubricants and 'di- 2-ethyl-4-me'thylpentanoatehas a -pour point of --75 C. compared with -60 C. for the di-Z-ethylhexoate.

2-alkyl-4-methylpentan0ls and 2-aZkyl-4-methylhexanols The isoenals produced by the condensation of the isoaldehydes (isobutyraldehyde and 2 methylbutyraldehyde) with 3, 4 and S-carbon aldehydes are reduced in the presence .of a suitable hydrogenation catalyst and at elevated temperatures and pressures to form the corresponding anols. These alcohols are particularly useful in the preparation of plasticizers, detergents and synthetic lubric'ants. For example, di-2-propyl-4-methylhexylphthalate is an excellent plasticizer for vinyl chloride and vinyl acetate resins. Similarly di-2-ethyl-4-methylpentylsebacate has excellent properties as a synthetic lubricant. It is also useful as a plasticizer for cellulose acetate-butyrate plastics. The 2-alkyle4-methylpentanols and 2-alkyl- 4-methylhexanols are formed by reducing the corresponding isoenals in the presence of a catalyst such as Raney nickel at temperatures ranging from to 200 C. and at elevated pressures in the range of 100-10,000

These new compositions of matter were prepared by the process illustrated in the following examples.

EXAMPLE .12

Five-hundred grams of 2-propyl-4-methylpentenal, 30 g. of Raney nickel and 50ml. of water were charged to a stainless steelrockin g autoclave. The autoclave was purged with hydrogen and heated to C. at 300 p. s. i. The reduction was complete in 2 hours and a 97% yield of 2-propyl-4-methylpentanol, boiling point 19219 2.5 C. was obtained. The percent hydroxyl (calculated) 11.80, found 11.81,

M from density and refractive index, calculated 45.12, theory 45.31.

EXAMPLE 13 molecular refractivity; calculated 49.82 1, theory 49.93, percent hydroxyl, found 10.8, theory 10.75.

EXAMPLE 14 In a similar manner 2-isopropyl-4-methylpentenal was hydrogenated in 99% yield to form 2-isopropyl-4-methylpentanol, boiling point 187 C. 2-ethyl-4-methylhexenal was hydrogenated in 93% yield to form 2-ethy1-4-methylhexanol, boiling point C.,

dgg 0.8303, Ni? 1.43313 TABLE I Boiling Poets of obhae'ns'ation Products at 760 mm. Isoaldehyde+Aldehyde Enals, Anals, V Anols,

' degrees degrees degrees centicenticentigrade grade grade n-butyraldehyde Q 2-ethyl-4-methylpentenal 164 153 176.5 isobutyraldehyde n-valeraldehyde 2-propyl-4-methylpentenal 178-9 170 192 3-methylbutyraldehyde 2-isopropyl-4-methylpentenal 175 166 187 prgpionalgelliyge; 2, t5111'1111ethyltlglexlefilal I 17? 16g 157 nu yra e y e 2e y 1-me y exena 18 17 2 methylbutyraldehyde 3-methy1butyraldehyd 2-is0pr0pyl-4-rnethylhexenal 192 183 202 n-valeraldehyde -2-propyl-4-methylhexenal 200 192 209 2-methylvaleraldehyde n-hexana1 2-butyl-4-methylhepteual 224 215 232 Dicarlioxylic acid esters of 2-alkyl-4-methylpentanols and 2-alkyl-4-methylhexanols Four-hundred grams of Z-propyl-4-methylhexanol, 148 grams of phthalic anhydride and 0.05 ml. of H 80 were heated to reflux in a round bottom flask equipped with a Dean-Stark trap. The theoretical quantity of Water, 18 ml., was removed rapidly and after distilling off the excess alcohol the remaining di-2-propyl-4-methylhexyl phthalate ester had an APHA color of 15. This ester is an excellent plasticizer for vinyl chloride and cellulose ester resins. Its boiling point is 173-176 C. at 0.15 mm.

EXAMPLE 16 Two-hundred twenty-five grams of 2,4-dimethylhexanol were mixed with 111 gm. phthalic anhydride and 0.1 ml. H 80 The mixture was heated at reflux until the theoretical amount of water had been collected in the water trap. The excess alcohol was removed by distillation to leave a faintly colored ester. The di-2,4-dimethylhexyl phthalate boils at l90-194 C. at 1.5 mm.

EXAMPLE 17 Two-hundred twenty-five grams of 2,4-dimethylhexanol were mixed with 50 grams succinic anhydride and 0.1 gm. p-toluenesulfonic acid in a flask equipped with a condenser and water trap. The mixture was refluxed until the theoretical amount of water was formed, the excess alcohol removed by distillation. The straw colored ester was distilled at reduced pressure to yield colorless product B. P. 151-155 C.

EXAMPLE 18 One-hundred forty-eight grams of phthalic anhydride, 320 grams of 2-propyl-4-methylpentanol and 0.2 gm. H 50 were mixed and heated at reflux until the theoretical amount of water had been obtained. The excess alcohol was removed by distillation at reduced pressure and the ester distilled to yield a very light colored product B. P. 203-207 (3.

EXAMPLE 19 One-hundred forty-six grams of adipic acid, 350 grams of 2-propyl-4-methylpentanol, and 0.05 ml. H 80 were mixed in a flask equipped with a condenser and water trap. This mixture was heated at reflux until 36 ml. of water had been collected. The excess alcohol was removed at reduced pressure to leave di-2-propyl-4-methylpentyl adipate which had an APHA color of 20. point of this ester is 193-197 C. at 1.2 mm.

EXAMPLE 20 The boiling One-hundred eighty-eight grams of azelaic acid, 350 gm;

2 -isopropyl-4-methylpentanol, and 0.05 ml. H were mixed and heated at reflux until the theoretical amount of water had been collected. The excess alcohol wasremoved by distillation to leave a lightly tinted ester B. P. L0 210-2l3 C.

EXAMPLE 2 1 Three-hundred fifty grams of 2-isopropyl-4 -methylpentanol and 202 gm. sebacic acid were treated with 0.05

gm. H 80 at reflux temperature until the theoretical amount of water 'had been collected. The excess alcohol was removed and the di(-2-isopropyl-4-methyl-)pentylsebacate distilled at reduced pressure to colored product B. P; 15 217-220" C.

EXAMPLE 22 yield a slightly One-hundred seventy-five grams of 2-ethyl-4-methylhexanol, 714 grams phthalic anhydride and 0.1 ml. H 80 were refluxed in a flask equipped with a Dean-Stark tube' until the theoretical amount of water was obtained. .The

excess alcohol was removed bydistillation and the ester was'distilled at reduced presure to give di-(2-ethvl-4- methyl)hexyl phthalate B. P. M 202-206 C.

EXAMPLE 23 EXAMPLE 24 Two-hundred grams of 2-propyl-4-methylhexanol, 50 grams of succinic anhydride and 0.1 gm. H 50 were mixed and heated at reflux until the theoretical amount of water had been collected in the water trap. The excess alcohol was removed and the residue distilled at reduced pressure to yield a water white ester di(2-propyl- 4-methylhexyl)succinate B. P. 1.5 -178 C.

The diesters of the present invention when used as plasticizers with vinyl resins and cellulose esters, such as cellulose acetate butyrate, also give higher values for tensile strength, per cent elongation and tear resistance. Comparative values for the phthalate esters of 2-ethyl-4- methylpentanol, 2-propyl-4-methylhexanol and other commercially available 8 and 10 carbon alcohols are shown in Tables II and HI. methylpentanol is compared with the well-known commercial Z-ethylhexanol. The 10 carbon 2-propyl-4-methylhexanol is compared with isodecanol produced by the oxonation of nonylene (propylene trimer).

The 8 carbon 2-ethyl-4-'v TABLE 11-50 P. H. R. IN GEON 101 Phthalate esters of- 8 and 10 carbon alcohols 2-propyl-4-metl1yl- 2-ethyl-4-meth yl- Reference hexanol lsodepentmiol Z-cthylcanol hexancl Tensile Strength 2, 800 2, 500 3, 450 3, 300 Elongation 380 270 370 330 Tear Resistance 420 320 460 330 Percent Loss Act. Cannon i 4 0. 6 1. 3 1.4

TABLE TIL-40 P. H. R. IN GEON 101 2-propyl-4-methyl- Q-ethyl-l-mo thyl- Reierence hoxanol isodc' pcntanol 2-ethylcanol hexanol Tensile Strength a, 250 s, 050 3, 850 a, 400 Elongation 400 370 310 290 Tear Resistance 610 530 560 400 Percent Loss Act. Carbon. (l. 2 0v 4., 1. l 1.1

The above results show that the 2-alkyl-4-methylpentanols and the 2-alkyl-4-mcthylhexanols have a definite superiority over previously available commercial plasticizer alcohols. Properties arelisted in Table IV for several other diesters and plasticizer alcohols produced according to the process of the present invention.

TABLE IV.-O P. H. R. IN GEON 101 Properties of plasticized vinyl We claim: l. A process for forming enals by the reaction of an isoaldehyde having 4-6 carbon atoms with a lower aliphatic aldehyde containing from 2-6 carbon atoms, which comprises reacting an excess of the isoaldehyde with the lower aliphatic aldehyde in the presence of a strongly alkaline catalyst and at temperatures ranging from -15 0 C.

2. A process for forming 2-alkyl-4-methylpentenals which comprises reacting an excess of isobutyraldehyde with a 2-6 carbon lower aliphatic aldehyde in the presence of a strongly alkaline catalyst at 60-150" C.

3. A process for forming 2-alkyl-4-methylhexenals which comprises reacting isovaleraldehydes with lower aliphatic aldehydes containing from 2-6 carbon atoms in the presence of a strongly alkaline catalyst at 60-150 C.

4. A process for reacting Z-methylvaleraldehyde and lower aliphatic aldehydes to form enals which comprises reacting excess isohexaldehyde with the lower aliphatic aldehyde containing from 2-6 carbon atoms in the presence of a strongly alkaline catalyst at 60-150 C.

5. The process according to claim 2 wherein n-butyr aldehyde is the lower aliphatic aldehyde and the anal produced is 2-ethyl-4-methyl pentenal.

.6. The process according to claim 2 wherein n-valeraldehyde is the lower aliphatic aldehyde and the enal produced is 2-propyl-4-methylpentenal.

7. The process according to claim 3 wherein propionaldehyde is the lower aliphatic aldehyde and the enal produced is 2,4-dimethy1hexenal.

8. The process according to claim 3 wherein n-butyraldehyde is the lower aliphatic aldehyde and the enal produced is 2-ethyl-4-methyl hexenal.

Kohn: Monatshcfte fiir Chemie, 22, pp. 21-58 (1901). Beilstcin: Band I, p. 707, 741 (1918). Burdick: I. Am. Chem. Soc., 56, 438-442 (1934). 

1. A PROCESS FOR FORMING ENALS BY THE REACTION OF AN ISOALDEHYDE HAVING 4-6 CARBON ATOMS WITH A LOWER ALIPHATIC ALDEHYDE CONTAINING FROM 2-6 CARBON ATOMS, WHICH COMPRISES REACTING AN EXCESS OF THE ISOALDEHYDE WITH THE LOWER ALIPHATIC ALDEHYDE IN THE PRESENCE OF A STRONGLY ALKALINE CATALYST AND AT TEMPERATURES RANGING FROM 60-150*C. 